1. Field of the Invention
The present invention relates to a semiconductor device in which a semiconductor element is flip-chip mounted on a circuit substrate.
2. Description of the Related Art
In recent years, reduction in the size and weight of semiconductor devices has been demanded in the field of electrical products, and especially portable equipment. For this reason, BGA (Ball Grid Array) and CSP (Chip Size Package) technologies are used in circuit substrates made of resin.
After flip-chip mounting a semiconductor element on a circuit substrate, the upper surface of the circuit substrate may be sealed with resin so as to cover the semiconductor element, with the aim of protecting the semiconductor element. Possible methods of sealing with resin are a method of sealing by injection molding using a die, or a method of sealing the upper surface of the circuit substrate by applying resin using a dispenser.
However, in this sealed semiconductor device, under normal temperature conditions, warping occurs which causes the center of the circuit substrate to become depressed, and, under high temperature conditions, warping occurs which causes the center of the circuit substrate to be mounded upwards. In a semiconductor device having large warping of this kind, the thickness of the semiconductor device becomes greater. Moreover, if this semiconductor device is mounted on another mother board, electrical connection defects occur between the semiconductor device and the mother board.
Japanese Patent No. 3420748 discloses a method which grinds the whole surface of a semiconductor device sealed with resin. FIG. 15A shows a semiconductor device before grinding. A semiconductor element 2 is bonded to a circuit substrate 4 by means of a flip-chip method, via a projecting electrode 3. An underfill resin 5 is disposed between the semiconductor element 2 and the circuit substrate 4, and the bond is maintained by the contraction of the underfill resin 5. The semiconductor element 2 mounted on the circuit substrate 4 is covered and sealed by a sealing resin 6 which is different from the underfill resin 5. Next, reduction of the thickness of a semiconductor device 1, as shown in FIG. 15B, is sought by grinding the whole surface of the sealing resin 6 until the semiconductor element 2 is exposed by back grinding, from the rear surface of the semiconductor element 2 (the upper side in FIG. 15B).
Japanese Patent Application Laid-open No. 2006-128488 proposes a method for applying the sealing resin 6 by a dispenser to the side surface of the semiconductor element 2 which is flip-chip mounted via the projecting electrode 3 to the circuit substrate 4, as shown in FIG. 16.
However, if the whole surface of the semiconductor device is ground until the rear surface of the semiconductor element 2 is exposed as shown in FIG. 15A and FIG. 15B, then the sealing resin 6 on the rear surface of the semiconductor element 2 and the sealing resin 6 surrounding the semiconductor element 2 are reduced, and therefore it is not possible to eliminate the problem of warping of the semiconductor device 1.
More specifically, under normal temperature conditions, warping occurs in the semiconductor device 1 in such a manner that the center of the circuit substrate 4 is mounded upwards, and under high temperature conditions, warping occurs in the semiconductor device 1 in such a manner that the center of the circuit substrate 4 is depressed. Consequently, electrical connection errors occur when the semiconductor device 1 is mounted on a mother board.
Furthermore, in the case of FIG. 16 where the sealing resin 6 is applied by a dispenser onto the side face of the semiconductor element 2, the height or width of the applied sealing resin 6 becomes instable and the amount of warping of the semiconductor device 1 fluctuates. Moreover, since the sealing resin 6 is applied by a dispenser, then the production tact time becomes longer.